The ignition of gaseous fuels, particularly in residential furnaces, have undergone extensive changes in order to improve efficiency. One major change that is currently underway is the replacement of a standing ignited pilot with some other type of ignition source. One of the more common ignition sources is a spark gap supplied with a high voltage to initiate a spark to ignite the gaseous fuel. This type of system is deemed to be fuel efficient in that fuel is consumed only when a demand for heat is placed on the heating system.
The application of a spark gap as an ignition source to a gaseous fuel has been well recognized for many years, but was not used extensively as the generation of a spark across the gap created many more problems than using a standing pilot as an ignition source. With the advent of the removal of the standing pilot as an efficient ignition source, the introduction of spark ignition has become widespread. With this comes certain types of installation and operating problems. The high voltage involved in generating a spark across a spark gap can create radio frequency interference, and has the potential for installation and service problems in handling the very high voltages involved. Typically, the voltage utilized in spark ignition systems for ignition of gaseous fuels is in the 12,000 to 16,000 volt range. At these voltages, voltage break down of conductor insulation, and voltage break down to unrelated surfaces can be a problem. Also, as previously noted, radio frequency interference is generated by the spark. It is desirable to lower the spark voltage as far as practical and still supply a reliable spark intensity across a gap that is not likely to be inadvertently bridged.